Fmds0131 Metal Roof Systems

5/27/2018 Fmds0131 Metal Roof Systems

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July 2008

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METAL ROOF SYSTEMS

Insureds of FM Global should contact the local FM Global office before beginning any roofing work.

Table of ContentsPage

1.0 SCOPE ................................................................................................................................................... 2

1.1 Changes .......................................................................................................................................... 2

2.0 LOSS PREVENTION RECOMMENDATIONS ....................................................................................... 2

2.1 Introduction ...................................................................................................................................... 2

2.2 Construction and Location ............................................................................................................... 2

2.2.1 General .................................................................................................................................. 2

2.2.2 Re-cover of Metal Roof Systems .......................................................................................... 3

2.2.3 Metal Roof Systems Used for Re-cover ............................................................................... 5

2.3 Operation and Maintenance ............................................................................................................ 63.0 SUPPORT FOR RECOMMENDATIONS ............................................................................................... 6

3.1 Additional Information ...................................................................................................................... 6

3.1.1 Structural Design ................................................................................................................... 6

3.1.2 Oriented Strand Board (OSB)/Composite Systems .............................................................. 6

3.1.3 Re-cover of Metal Roof Systems .......................................................................................... 7

3.1.4 Metal Roof Systems Used for Re-cover ............................................................................... 8

3.1.5 Roof Areas Needing Increased Fastening ............................................................................ 8

4.0 REFERENCES ...................................................................................................................................... 11

4.1 FM Global ....................................................................................................................................... 11

4.2 Others .............................................................................................................................................. 11

APPENDIX A GLOSSARY OF TERMS ....................................................................................................... 11

APPENDIX B DOCUMENT REVISION HISTORY ..................................................................................... 11

APPENDIX C SUPPLEMENTARY INFORMATION ................................................................................... 12

C.1 Metal Panel Types ........................................................................................................................ 12

C.1.1 Standing Seam and Lap Seam Roofs ................................................................................ 12

C.1.2 Insulated Roof Deck Panels ............................................................................................... 13

C.2 OSB/Composite Systems ............................................................................................................. 13

C.3 Re-cover of Metal Roof Systems .................................................................................................. 13

C.4 Metal Roof Systems Used for Re-cover ....................................................................................... 13

List of FiguresFig. 1. Typical re-cover of existing standing seam roof. ................................................................................ 4

Fig. 2. Standing seam roof in re-cover construction. ..................................................................................... 5

Fig. 3. Standing seam roof applied to OSB/composite insulation. ................................................................ 7

Fig. 4. Attachment utilizing bar secured to existing metal panel. Courtesy of Goodyear Tire & Rubber Co.. 10

Fig. 5. Clip secured to purlinCourtesy of Vic-West Steel Co. .................................................................. 10

Fig. 6. Standing seam clipCourtesy of Vic-West Steel Co. ..................................................................... 12

List of TablesTable 1. Recommended Rating of Field, Perimeter, and Corner Areas (Zones 1, 2, and 3)

for Enclosed Buildings3 .................................................................................................................... 9

FM GlobalProperty Loss Prevention Data Sheets 1-31

2008 Factory Mutual I nsurance Company. All rights reserved. No part of this document may be reproduced,stored in a retrieval system, or transmitted, in whole or in part, in any form or by any means, electronic, mechanical,photocopying, recording, or otherwise, without written permission of Factory Mutual Insurance Company.


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1.0 SCOPE

This data sheet provides recommendations for the installation and maintenance of metal roof systems.Information is included on new construction, re-cover of existing metal roof systems, and use of metal roofsystems in re-covering existing low-sloped roofs. The generic termmetal roof system is used throughout this

data sheet when discussing all three types of systems (standing seam and lap seam roof systems andinsulated roof deck panel systems), except where noted. Guidance is also given for those situations whereFM Approved (see Appendix A for definition) products are unavailable.

Information and recommendations are applicable to all three types of metal roof systems unless notedotherwise. Refer to the Approval Guide(a publication of FM Approvals) and RoofNav (web-based softwareby FM Approvals) for additional details and ratings on these systems.

1.1 Changes

July 2008. Table 1 was made consistent with revisions in Data Sheet 1-28, Wind Design, and Data Sheet1-29,Roof Deck Securement and Above-Deck Roofing Components. This change raised the safety factor inthe perimeter and corner areas to 2.0. Prescriptive perimeter and corner enhancements remain unchanged.Recommendation 2.2.4 relating to gravity loads was added.

2.0 LOSS PREVENTION RECOMMENDATIONS

2.1 Introduction

The recommendations in this data sheet are not intended to supersede the requirements of any priorFM Approval. They should be used to supplement the RoofNav listings. For all applications, follow the generalrecommendations (Section 2.2.1). If applicable, follow the specific recommendations (Sections 2.2 and 2.3).

2.2 Construction and Location

2.2.1 General

2.2.1.1 Install appropriate wind uplift rated, FM Approved metal roof systems, where available. Secure thesystem in the roof field in accordance with RoofNav and the Approval Guide, a publication of FM Approvals.Use components that are FM Approved for use together. Use of FM Approved components and systems

is universally recommended and is implied for all applicable assemblies whether or not specifically stated.

2.2.1.2 Do not accept materials without proper FM Approval labeling. All FM Approved materials are requiredto have the FM Approval mark on the packaging or the material itself.

2.2.1.3 Determine design and factored (rated to include safety factor) field of roof wind uplift pressure inaccordance with Data Sheet 1-28.

2.2.1.4 Use Table 1 to determine the FMApproved wind uplift rating for the roof system, including the perimeterand corner areas, as higher uplift forces on these areas result in the need for additional securement overthat FM Approved for the field of the roof. Alternatively, use prescriptive perimeter and corner enhancementsper Section 3.1.5. Refer to Data Sheet 1-28, Wind Design, for corner/perimeter definitions, dimensions, andexamples.

Provide increased deck securement to the next purlin support and/or deck seam where the perimeter/cornerwidth falls between purlin supports or deck rib seams.

2.2.1.5 Ensure metal roof systems are designed for snow and rain loading and drainage in accordance withData Sheet 1-54, Roof Loads for New Construction.

2.2.1.6 Ensure metal roof systems have a minimum slope of 14 in./ft (21 mm/m). Steeper minimum slopesmay be recommended by the roof system manufacturer, particularly for lap seam roofs.

2.2.1.7 For lap seam and standing seam metal panel roofs installed over oriented strand board/foam plasticcomposite (OSB/composite) insulation, use only FM Approved standing or lap seam roof systems. Currently,there are no FM Approved combinations of metal roofs over OSB/composite; however, such installationsmay be acceptable if installed in accordance with Recommendations 2.2.1.7, 2.2.1.8, and 2.2.1.9.

2.2.1.8 Use only FM Approved OSB/composite insulation with lap seam and standing seam metal roof. Ensureit secured to the supporting roof deck per the Approval Guide. Ensure the OSB layer is a minimum of 58

1-31 Metal Roof SystemsPage 2 FM Global Property Loss Prevention Data Sheets

2008 Factory Mutual Insurance Company. All rights reserved.


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in. (16 mm) thick. Determine the spacing of the FM Approved metal roof system fasteners applied over the

OSB/composite from pull-out tests as outlined in Section 3.1.2.

2.2.1.9 For lap seam and standing seam roofs, when the supporting roof deck for OSB/composite insulation

is steel, ensure it is FM Approved, 18-22 ga (0.0474-0.0295 in. [1.204-0.749 mm]), installed per theApproval

Guideand Data Sheet 1-28, Wind Design.2.2.1.10 For protection of new or re-cover construction of metal roof systems installed adjacent to Maximum

Foreseeable Loss (MFL) fire walls, refer to Data Sheet 1-22, Criteria for Maximum Foreseeable Loss Fire

Walls and Space Separation.

2.2.1.11 Do not use perforated liner panels in metal roof systems where the occupancy uses or produces

a considerable amount of dust, oil, or oil mist. There have been cases where the dust or oil has collected inside

the panels, greatly increasing the fire spread potential.

2.2.1.12 Provide roof-top walkways in areas subject to frequent foot traffic to avoid damage to the roof system.

2.2.1.13 Provide thorough supervision by the building owners qualified representative during all roofconstruction to ensure quality of workmanship and adherence to FM Global data sheets and project

specifications.

2.2.2 Re-cover of Metal Roof Systems

2.2.2.1 If the existing metal roof deck is aluminum, consider it Class 2 when re-covered (an exception is

an existing glass fiber insulated Class 1 aluminum system re-covered with another metal panel system). When

the roof deck is aluminum, (not necessary with steel roof decks) remove any existing batt-type insulation

(standing and lap seam roofs) or have it held in place with steel liner panels (do not use expanded metal or

wire mesh) to avoid shielding of sprinkler water.

Provide automatic sprinklers below all Class 2 deck. Ensure the existing batt insulation is tight to the underside

of steel decks, with no significant air space (2 in., 50 mm, or less).

See Data Sheet 1-29,Above-Deck Roof Components, for additional information on Class 2 roof decks. Follow

the manufacturers instructions as to whether the fasteners should be driven into or through aluminum forthis purpose. Ensure the manufacturer confirmed that the fastener/aluminum combination is not susceptible

to galvanic corrosion.

2.2.2.2 Ensure the new roof cover (single-ply membrane or liquid-applied coating system) is specifically FMApproved for re-cover construction on the existing type of metal roof system (standing seam, lap seam, or

insulated metal panel).

2.2.2.3 Where constructions specified in recommendation 2.2.2.2 are not available, it is acceptable to re-cover

a metal roof system with a row-attached (batten bars or in-seam fasteners), FM Approved single-ply roof

cover, provided the following is done:

a. For standing seam roofs: Apply two layers of FM Approved insulation. Use perlite or polyisocyanurate

insulation for the lower layer. Ensure the thickness is the height of the seams (see Fig. 1). Do not use

other insulation types unless specifically FM Approved for this use. Ensure the upper layer is specifically

FM Approved for use with the roof cover. In the case of a polyisocyanurate lower layer, ensure the top

layer is either FM Approved wood fiber or a FM Approved thickness of the same polyisocyanurate. Ensure

the total insulation thickness does not exceed the maximum FM Approved thickness of the

polyisocyanurate insulation.

b. For lap seam roofs: Apply FM Approved polyisocyanurate insulation over the roof. Ensure the insulation

thickness is sufficient to span the rib openings (See Data Sheet 1-28). If the profile is similar to a standing

seam roof, install the insulation per aabove. Ensure the insulation is specifically FM Approved for usewith the roof cover.

c. For FM Approved foam plastic insulated panels: To maintain the Class 1 rating, cover the panel with

a maximum of 1 in. (25 mm) of FM Approved insulation that is specifically FM Approved for use with the

roof cover.

Metal Roof Systems 1-31FM Global Property Loss Prevention Data Sheets Page 3



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d. Have the insulation(s) pre-secured in the field of the roof with FM Approved insulation fasteners (through

both layers, if applicable) at 1.5 times the rate recommended for 22 ga (0.0295 in., 0.749 mm) steel deck

(i.e., the rate is three fasteners per board for boards up to 4 4 ft [1.2 1.2 m], and six fasteners per

board for boards up to 4 8 ft [1.2 2.4 m]).

e. Have the rows of roof cover fasteners run over and driven directly into the purlins. Use a self-drillingtype, adequate for the thickness of the purlin flange. Apply the fasteners in the field of the roof at the

spacing FM Approved for 22 ga (0.0295 in., 0.749 mm) steel deck.

2.2.2.4 For all re-roofing applications, the new roof will add additional weight to the structure. Have the

structure analyzed to ensure that it can support the anticipated loads without reducing the live load capacity

below acceptable limits.

2.2.2.5 For liquid-applied coating re-cover systems, complete surface preparation of the existing metal roof

with strict adherence to the coating manufacturers specifications. To meet FM Approval requirements,minimum/maximum slope requirements and coating application rates must be observed.

2.2.2.6 Do not apply spray-applied polyurethane foam directly to the top of metal roof systems unless a

Class 2 deck can be tolerated. Ensure the following are true before accepting a Class 2 deck:

a. The building is sprinklered.

b. There are no Class 2 roof deck MFL considerations.

c. Batt insulation below the deck is removed or held in place (tight to the deck underside, with no air

space) with steel liner panels (expanded metal or wire mesh is not acceptable).

Refer to Data Sheet 1-29, Above Deck Roof Components, for additional information on Class 2 roof decks.

Refer to Data Sheet 1-57, Plastics in Construction, for details on the installation of polyurethane foam.

2.2.2.7 Provide roof areas that have increased uplift pressures with increased fastening as outlined in Section

3.1.5.

Fig. 1. Typical re-cover of existing standing seam roof.




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2.2.3 Metal Roof Systems Used for Re-cover

Insulated roof deck panel systems are not usually used for this application. Hence, the recommendations

in this section are not applicable to these systems.

2.2.3.1 When a metal roof system is installed over an existing built-up roof (BUR), a combustible concealed

space can be formed (Fig. 2). Therefore, do one of the following. Also, use noncombustible framing for thenew roof, except as noted.

a. If the existing BUR has an American Society for Testing and Materials (ASTM) E 108 Class A-rated

mineral surfaced cap sheet or is gravel surfaced and the gravel will remain, no other protection is needed.

If the existing roof is Class 1 insulated steel deck, add no more than 1 in. (25 mm) of additional

noncombustible insulation (glass fiber, mineral wool, FM Approved noncombustible board stock) over the

existing graveled BUR; otherwise, the Class 1 rating may be compromised.

b. Remove the existing BUR, insulation, and adhesive down to the bare steel deck. Note: if the existing

deck is wood, have it covered with minimum 12in. (13 mm) thick gypsum board (ordinary gypsum boardis acceptable) prior to installation of the framing system.

c. If the existing BUR is smooth surfaced and the deck is Class 2 insulated steel deck or concrete, protect

the roof cover with a minimum of 6 in. (152 mm) of unfaced glass or mineral fiber batts. Do not use thisoption if the existing deck is Class 1 insulated steel deck, as the additional insulation would probably

cause the deck to be Class 2.

d. Provide dry-pipe, automatic sprinklers can in the space. Consider this option only if there will be

sufficient access (e.g., hatchways in the existing roof) to the sprinkler system. Also, the new and existing

framing must be capable of supporting the additional weight. Ensure the new framing does not obstruct

the flow of sprinkler water to the existing roof drains. Combustible framing can be used.

2.2.3.2 Fill the expansion joints in the existing roof with ceramic or mineral fiber and cover with minimum

22 ga (0.0295 in., 0.749 mm) sheet steel fastened in place. Ensure the steel is designed to allow for

movement.

Fig. 2. Standing seam roof in re-cover construction.




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2.2.3.3 Ensure framing for the metal roof system is adequately supported by the existing bar joists. That is,

it is not supported by the steel deck at midspan.

2.2.3.4 Remove all wet insulation in the existing roof system. For details on wet insulation see Data Sheet

1-29,Above Deck Roof Components.

2.2.3.5 The new roof system and framing will add additional weight to the structure. The increase may beoffset by removing any existing gravel surfacing or above-deck components (see recommendation 2.2.3.1

above). In all cases, analyze the structure to ensure it can support the anticipated loads.

2.2.4 For new construction of standing seam metal roof systems on cold-formed steel C or Z purlins, ensure

the design is in accordance with the 2007 version of the American Iron and Steel Institute (AISI) standard,

North American Specification for the Design of Cold-formed Steel Structural Members. For locations outsidethe United States, comparable local specifications may be followed, provided the design of purlins considerestheir lateral support using one of the following methods:

1. The purlin capacity used in the design accounts for unbraced length between purlin braces.

2. The purlin capacity used in the design is based on testing that similates the lateral resistance provided

by the actual deck and clip assembly.

2.3 Operation and Maintenance

2.3.1 Provide regular maintenance of gutters and parapets to keep them clear of snow, ice, and debris

accumulations. Use open-channel (three-sided) conductors (leaders, downspouts) in areas where multiple

snow storms can be expected in any given winter season. Another option is to truncate down-spouts above

potential snow banks or points of possible vehicle impact (parking areas, truck docks, etc.). Remove snow

and ice accumulations around closed conductors. Use heat tracing and/or open-channel conductors for

gutters and conductors with a history of ice blockage.

3.0 SUPPORT FOR RECOMMENDATIONS

3.1 Additional Information

3.1.1 Structural Design

The wind-load design of metal roof systems built to other specifications may not be as stringent as thoseconforming to FM Approval requirements and the recommendations in this data sheet. The design uplift

pressures for each installation should be per Data Sheet 1-28, with enhancements as recommended in this

document.

Roof deck and purlins or bar joists are typically designed for uniformly distributed loads. Constructing a

framing system above the existing deck to support a re-cover system may load the structure with point

(concentrated) loads. This loading is usually a more critical case. The analysis must take into account any

concentrated live, snow, wind, and dead loads from the new standing seam system, plus the distributed dead

loads from the existing roof.

When designing a new metal roof system, it may be prudent to include an allowance for future dead loads

due to possible re-cover construction. Otherwise, future re-cover options may be limited to coating systems

or panel replacement. If, however, these future options are deemed sufficient, an additional allowance would

not be cost effective.

3.1.2 Oriented Strand Board (OSB)/Composite Systems

Most OSB/composite insulations (see Fig. 3) listed in the Approval Guideare FM Approved for use with BUR

covers. With regard to internal firespread, a standing seam or lap seam metal roof is less critical than a BUR.

Hence, if one of these systems is installed directly over an FM Approved OSB/composite on steel deck, the

construction can be considered Class 1.

To ensure adequate wind uplift resistance, secure the OSB/composite to the deck as FM Approved for BUR

construction with the appropriate wind uplift rating. The FM Approved metal roof system is then secured to

the OSB top surface. It is necessary to run pull-out tests of the metal roof system fasteners driven into the OSB

board to determine the necessary fastener spacing. This is because the pull-out resistance of the OSB board




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would most likely be less than that of steel purlins for which the FM Approved metal roof system was designed.

Once the pull-out resistance is known, field-of-roof fastening density can be determined as outlined below.

In no case should the metal roof fastener spacing be less than the FM Approved spacing for direct securement

to purlins. By limiting these constructions to FM Approved metal roof systems, failure modes other than

fastener pull-out are already accounted for. Hence, fastener spacing can be based on fastener pull-out

resistance. As an option, pull-out tests can be run in the laboratory on representative samples. The procedure

for determining the roof clip fastening density for this construction using FM Approved metal roof systems

is as follows:

1. Factored wind uplift pressure is determined from Data Sheet 1-28 or applicable design guideline,

whichever is more stringent.

2. Fastener pull-out resistance from the OSB board is obtained. A minimum of three tests are run with the

average value taken as the resistance.

3. Allowable area/fastener is calculated by dividing pull-out strength by the factored uplift pressure per Data

Sheet 1-28 as follows:maximum area per fastener = (pull-out strength)/(factored uplift pressure).In no case

should the spacing be less than that FM Approved for roof securement direct to purlins.

4. The roof corner/perimeter/peak fastener density is increased over the field density per Section 3.1.5.

3.1.3 Re-cover of Metal Roof Systems

Not all FM Approved insulation types are recommended in re-cover construction of metal roof systems

because testing has shown that some insulations (even if Approved with 22 ga [0.0295 in., 0.749 mm] deck)

can create a Class 2 roof when used to re-cover metal roof systems. Use only insulations noted in the

recommendations, specifically FM Approved for re-cover of metal roof systems, or qualified via FM Global

Construction Materials Calorimeter testing. However, if a Class 2 roof is tolerable ( per Data Sheet 1-29), any

insulation compatible with the roof cover can be used. In all cases, the external fire spread potential (ASTM

E 108 rating) should be known or determined. See Data Sheet 1-29 for information regarding E 108 ratings.

Single-ply roof cover fasteners FM Approved for conventional re-cover systems are designed for use in

minimum 22 ga (0.0295 in., 0.749 mm) steel deck. Adequate pull-out resistance would not be obtained if

they were driven into thinner 24-26 ga (0.0237-0.018 in., 0.607-0.457 mm) metal roof systems. Installing the

fasteners into the thinner panels at a density greater than that for 22 ga (0.0295 in., 0.749 mm) steel deck

based on static pull-out tests alone is not reasonable. The thin metal panels may allow excessive fastener

fatigue (back-out or pull-out) due to roof cover fluttering in mild winds. Adequate securement can be obtained

by driving the roof cover fasteners into the purlins.

Fig. 3. Standing seam roof applied to OSB/composite insulation.




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The fastening density for securing insulation to these thinner decks with mechanically-secured, single-ply

roof covers should be 50% greater than that recommended for 22 ga (0.0295 in., 0.749 mm) steel deck. The

reason for the higher density is that fastener pull-out resistance in the thinner metal panels is less than that

obtained with 22 ga (0.0295 in., 0.749 mm) steel deck. Fastener fatigue is not considered a major concern

for insulation fasteners because the insulation is not subject to the same cyclic loading as the mechanically

secured roof cover.

FM Approved liquid-applied coatings and polyurethane foam systems FM Approved for spray-applied,

direct-to-steel deck may be used to re-cover existing metal roof systems. For coatings, re-tightening the

fasteners, reinforcing the joints with fabric, wire brushing rusted areas, and power washing the roof are usually

needed (and required by the coating manufacturer) prior to coating application. Some coatings have minimum

and maximum slopes for which they are FM Approved. The minimum slope requirement is needed as some

coatings are not tolerant of ponded water. The maximum slope requirement is needed to limit exterior flame

spread.

Non-Approved polyurethane foam spray-applied directly to existing metal roof systems could constitute a

Class 2 roof deck. If a Class 2 deck is tolerable, this may be acceptable. Refer to Data Sheet 1-29 for

information on Class 2 roof decks.

3.1.4 Metal Roof Systems Used for Re-cover

The additional insulation over existing Class 1 steel and wood decks is limited to 1 in. (25 mm) because

tests have shown that greater thicknesses can cause the deck to be Class 2. Filling the existing expansion

joints with mineral fiber is intended to reduce fire spread through the roof deck in either direction.

3.1.5 Roof Areas Needing Increased Fastening

As noted in Data Sheet 1-28, increased fastening of roof systems is needed at the roof corners and perimeter

due to the higher uplift pressure in these areas. Higher uplift pressure also occurs at the roof peak on roofs

sloped greater than 7(1.5 in./12 in. [38 mm/305 mm]). Use the methods outlined below to increase fasteningdensity in the specific areas recommended in Data Sheet 1-28.

Data Sheet 1-29 outlines the recommended methods of increasing the fastening density of mechanically

secured single-ply roof covers. The basic recommendation is that increased fastening is achieved by

decreasing the distance between fastener rows rather than between fasteners in each row. This method

allows a reduced and more even distribution of fasteners; it also reduces the membrane span. It is not apractical method for some metal roof systems, however, so other means are used.




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Use one of the following three methods for increasing the securement of the roof system in the roof perimeter

and corners:

1. Use a roof system with the appropriate FM Global wind uplift rating in each area per Table 1, or

Table 1. Recommended Rating of Field, Perimeter, and Corner Areas (Zones 1, 2, and 3) for Enclosed Buildings3

Roof Field Area Design

Pressure, p, (psf)2

Minimum Wind Rating for FM Approved Deck/Above-Deck/Entire1 Assembly

Roof Field Area Enclosed

Bldg.

Roof Perimeter Area

Enclosed Bldg.

Roof Corner Area Enclosed

Bldg.

P 30 60 105 150

30 < p 37.5 75 120 180

37.5 < p 45 90 150 225

45 < p 52.5 105 180 270

52.5 < p 60 120 195 300

60 < p 67.5 135 225 330

67.5 < p 75 150 255 360

75 < p 82.5 165 270 405

82.5 < p 90 180 300 435

90 < p

97.5 195 315 48097.5 < p 105 210 345 510

105 < p 112.5 225 360 540

112.5 < p 120 240 390 585

120 < p 127.5 255 420 615

127.5 < p 135 270 435 660

1 Base the minimum wind rating on the roof field area rating when perimeter/corner areas are enhanced per this data sheet and other pertinentFM Global data sheets (1-29, 1-31, etc.). Base the minimum wind rating on the respective area rating (field, perimeter, corners) whenperimeter/corner area enhancements in this document are not proposed, or are not acceptable.2 For roofs with higher field area design pressures, or to interpolate needed perimeter and corner ratings when the field requirements arebetween levels, multiply the needed field area design pressure from Table 3, 4 or 5 (of DS 1-28) by a safety factor of 2.0 and the respectivepressure coefficient for perimeter and corner areas (see Table 6), and round up to the next highest 15 psf rating interval.3 Ratings above apply to roof slopes 7 and roof heights 60 ft (19 m).

2. Use the FM Approved proprietary perimeter and/or corner fastening method, (if one exists), listed for the

manufacturer, or

3. Use the appropriate prescriptive recommendation listed below. Note: The increase in fastening is applied

to the field of roof fastening listing in the Approval Guide.

A. Single-Ply Re-cover System Secured Through Existing Metal Panel Roofs Directly to Purlins

It is not practical to provide additional rows of fasteners for re-cover systems in which the mechanically-

attached, single-ply roof cover is secured directly to the purlins because the existing purlins usually are a

fixed distance of 4 to 6 ft (1.2-1.8 m) on center. For these cases, it would be acceptable to increase the

fastening density of the new single-ply roof cover by decreasing the spacing between fasteners along each

fastener row or batten bar in the noted areas. The fastener spacing is a maximum of 60 percent and 40

percent of the FM Approved spacing (for the field of roof) in the perimeter and corners respectively, but no

closer than 3 in. (76 mm). If there are additional purlins in the areas needing increased fastening, the fastening

of the single-ply membrane can be increased per Data Sheet 1-29. Increase pre-securement of the insulation

(Recommendation 2.2.2.3, item d) by 50% in these areas.

B. Proprietary Single-Ply Re-cover System Attached Directly to Existing Metal Roof System Panels

For FM Approved proprietary re-cover systems in which the new single-ply roof cover is secured to bars

(rails) attached to the metal roof (Fig. 4), decrease the distance between fastener rails per Data Sheet 1-29

in the noted areas. In these systems, the base rails are attached to the metal panels directly over the standing

seams. Hence, where necessary, round spacing down to the next standing seam. Increase pre-securement

of the insulation (Recommendation 2.2.2.3, item d) by 50% in these areas.

C. New Construction Standing Seam Roof Secured to Purlins

For new construction of standing seam roofs secured directly to purlins, the clips are installed at each

purlin/seam intersection (Fig. 5). Therefore, it would not be possible to increase the number of clips without




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increasing the number of purlins or using narrower panels. Using narrower panels on only the perimeter or

corners of the roof is not practical. Increased fastening can be accomplished by installing additional purlins

in the noted areas. Space these purlins a maximum of 12 and 1/3 times the spacing in the field of the roof inthe perimeter and corners respectively.

Example: Field of roof purlin spacing of 5 ft (1.5 m) would have perimeter spacing of 2.5 ft (0.76 m) andcorner spacing of 1.67 ft (0.5 m).

Fig. 4. Attachment utilizing bar secured to existing metal panel. Courtesy of Goodyear Tire & Rubber Co.

Fig. 5. Clip secured to purlinCourtesy of Vic-West Steel Co.




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D. New ConstructionStanding Seam and Lap Seam Roof Secured to OSB/Composite

For metal roof systems secured to OSB/composite board, ensure the spacing between clips along the panel

joints is a maximum of 12 and 1/3 times the spacing in the field of the roof in the perimeter and cornersrespectively. Increase the fastening of the OSB/composite board per Data Sheet 1-29, assuming a fully

adhered roof cover has been installed.E. Lap Seam Roof Systems

With lap seam roofs, it may be acceptable to have constant purlin spacing across the entire roof and reduce

the spacing between fasteners in the perimeter and corners to no more than 60% and 40%, respectively,

of that needed for the field of the roof along each purlin. Another option is to fasten the panels to intermediate

purlins or sub-purlins in the noted areas per Cabove. For new construction, ensure the panel span doesnot exceed that allowed by the manufacturer for the design wind load (one half that of Table 1)

F. New Construction Insulated Roof Deck Panels

Treat systems using clips per Cabove. Treat systems using through-bolting per Eabove.

4.0 REFERENCES

4.1 FM Global

Data Sheet 1-22, Maximum Foreseeable Loss Limiting Factors.

Data Sheet 1-28, Wind Design.

Data Sheet 1-29, Roof Deck Securement and Above-Deck Roof Components.

Data Sheet 1-54, Roof Loads for New Construction.

Data Sheet 1-57, Plastics in Construction.

4.2 Others

American Iron and Steel Institution (AISI)

American Iron and Steel Institute (AISI). AISI Cold-Formed Steel Design Manual. AISI TS-8-02, Base Test

Method for Purlins Supporting a Standing Seam Roof System. Latest edition.

American Iron and Steel Institute (AISI). North American Specification for the Design of Cold-Formed Steel

Structural Members. Latest edition.

APPENDIX A GLOSSARY OF TERMS

Also see Data Sheet 1-28 for additional explanation of teams related to wind design.

FM Approved: References toFM Approved in this data sheet mean the products or services have satisfiedthe criteria for FM Approvals. Refer to the Approval Guide, a publication of FM Approvals, for a complete

listing of products and services that are FM Approved.

Metal roof system(MRS): As used in this document, the term refers to standing seam and lap seam roof

systems, and insulated roof deck panel systems.

APPENDIX B DOCUMENT REVISION HISTORY

July 2008. Table 1 was made consistent with revisions in Data Sheet 1-28, Wind Design, and Data Sheet

1-29,Roof Deck Securement and Above-Deck Roofing Components. This change raised the safety factor in

the perimeter and corner areas to 2.0. Prescriptive perimeter and corner enhancements remain unchanged.

Recommendation 2.2.4 relating to gravity loads was added.

May 2003. Clarifications were made to recommendations in the Section 2.2.3,Metal Roof Systems Usedfor Re-cover.

May 2002. Clarification was made to recommendation 2.2.2.1 under Section 2.2.2, Re-cover of Metal Roof

Systems.




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January 2000. That revision of the document was reorganized to provide a consistent format and to

consolidate related Engineering Bulletins.

January 1999. Table 1 was completely revised.

June 1996. Editorial changes were made.

June 1992. First edition of Metal Roof Systems.

APPENDIX C SUPPLEMENTARY INFORMATION

C.1 Metal Panel Types

There are three basic types of metal roof systems: lap seam, standing seam, and insulated roof deck panel

systems.

C.1.1 Standing Seam and Lap Seam Roofs

These metal roof systems are formed using 22-26 ga (0.0295-0.018 in., 0.749-0.457 mm) steel. Copper and

aluminum may also be used for standing seam panels. Steel panels are usually coated with zinc or

zinc-aluminum alloys and/or painted to minimize corrosion. Standing seam panels are usually 12-24 in.

(305-610 mm) wide. Lap seam panels are generally wider, about 48 in (1.2 m). The limiting factor for panellength is usually transportation restrictions.

For new construction, the panels are usually secured to supporting members called purlins. The purlins are

CorZshaped cold-rolled members. They are usually 12-16 ga (0.105-0.059 in., 2.667-1.500 mm) steel.In some cases, bar joists are used.

Lap seam roofs are cold-formed steel panels that are fastened directly to the purlins with self-drilling fasteners.

The fasteners are driven through the panels into the purlins. The fasteners include a washer under the head

to seal against leakage. A sealant may be applied within the laps to provide waterproofing. FM Approved

systems are listed in the Approval Guide within the Protected Metal Panel and/or Panel Roof Covering

sections. Lap seam roofs are usually corrugated but can be formed with large flat areas between the ribs,

resembling standing seam panels.

A potential problem with this type of roof is that movement caused by thermal expansion can induce stress

on the fasteners and panel joints. Screw holes can become elongated and the sealants in the panel jointscan crack. Both situations can cause leaks.

Standing seam roofs also consist of cold-formed metal panels, but they are not through-fastened to the purlins.

Instead, clips (Fig. 6) are fastened to the purlins. The panel is then secured to the clips within the panel joints

(Fig. 5). The edges of the panels form a tight seal, 2-4 in. (51-102 mm) above the flat portion of the roof.

Some systems include a sealant in the joint. Under usual conditions, this keeps the seam above the level of

water on the roof and maintains water tightness. However, if gutters or downspouts become blocked, leakage

can occur. The concealed clips do not penetrate the panel and allow for movement caused by thermal

expansion.

Fig. 6. Standing seam clipCourtesy of Vic-West Steel Co.




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The standing seam panels can be joined using a proprietary machine or hand tools. These seams are formed

in one of two ways: panel edges can be folded over each other, or a separate strip (batten) can be put over

the two edges and crimped together. A third type of joint does not incorporate crimping. The panels simply

snap together when installed. Currently, there are no snap-together systems FM Approved. The end laps of

all types are usually simple overlaps and are screwed together with a sealant applied between the layers.

Adequately sized and fastened clips can provide the necessary wind uplift resistance while allowing the panels

to move in the longitudinal direction. To accommodate this movement, only one end of the panels is

restrained. Typically, the panels are secured with through-fasteners at the eave line and clip fasteners in the

field of the roof. This allows the roof to expand at the ridge. Ridge caps are designed to accommodate this

movement.

Both roof types are usually insulated on the underside with glass fiber batts and a vapor retarder. A metal

liner panel may also be installed on the underside. The liner is usually of thinner gage than the roof panel.

In most systems, the liner does not add uplift strength to the assembly.

C.1.2 Insulated Roof Deck Panels

A variation of the above systems is the insulated metal sandwich panel that consists of metal skins with a

foam plastic or paper and/or aluminum foil honeycomb core. These are typically factory assembled. They can

be attached with clips, similar to standing seam roofs or through fastened. FM Approved panels are listedin the Approval Guideunder the Panel Roof Coverings category.

C.2 OSB/Composite Systems

A common installation for standing seam roof systems consists of an OSB/composite insulation mechanically

secured to standard FM Approved deep steel roof deck. The standing seam clips are then fastened to the

OSB top surface of the insulation. Typical OSB/composites have a 7/16 in. (11 mm) thick OSB top surface that

offers considerably less fastener pull-out resistance than steel purlins. The minimum recommended OSB

thickness for this application is 58 in. (16 mm).

Currently, there are no FM Approved combinations of metal panels and OSB/composite insulations.

C.3 Re-cover of Metal Roof Systems

Metal roof systems are commonly re-covered with coatings or single-ply roof cover systems. Many existingmetal roofs are 24-26 ga (0.607-0.457 mm); hence, adequate mechanical securement to the roof panel itself

is difficult. Single-ply systems specifically FM Approved for re-cover over existing metal roof systems should

be installed and fastened as FM Approved in the field of the roof and enhanced as outlined at the corners

/perimeter/peak.

C.4 Metal Roof Systems Used for Re-cover

Metal roof systems may be used to re-cover existing low sloped BUR systems. For these installations, a

framing system is constructed over the existing BUR (Fig. 2). It may be necessary to remove the gravel

surfacing to reduce the dead load to the structure. The framing supports are secured through the existing roof

covering to the deck. The new metal roof system is then secured to the framing. This installation allows for

improved drainage as the new standing seam system can (and should) be sloped.



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Fmds0131 Metal Roof Systems